Gear-cutter.



T. FAWGUS.

GEAR CUTTER.

APPLICATION FILED AUG. 6, 1912.

1,096,163, Patented May 12,1914.

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NNNNNN OR 'rnn STATES GEAR-C 1,096,163. Specification of Application filed August 6,

T 0 (ZZZ whom it may concern Be it known that I, THOMAS FAWCUS, a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement 111 Gear-Cutters, of which the followin is a full, clear, and exact description, re erence being had to the accompanying drawlngs, forming part of this specification, in which:

Figure 1 is a view partly in side elevation and partly in lineal section of a hob embodying my invention; Fig. 2 is an end view of the hob; Fig. 3 is a plan view ofthehob proper; Figs. 4 and 5 are perspective views of the end or driving members; Fig. 6 is a detail sectional view showing one of the cutting teeth of the hob in elevation; and Fig. 7 is a plan view of one of the .teeth. F 1g. 8 is a longitudinal sectional view showing a modification.

My invention has relation to that class of gear cutting tools, and particularly to cutters, commonly known as hobs which are employed in the manufacture of helical gears and the like.

Prior to my invention hobs have generally been made in two forms, namely, the shell form, and the form, made in one solid piece. In the shell form, the diameter is great enough to provide an opening for receiving the hob driving shaft which extends therethrough. This driving shaft is neces sarily rigid, and is required to be of relatively large diameter, and the hole formed in the hob to receive it is necessarily of such diameter as to largely weaken the hob unless it is made of large diameter. It is usually desired to keep the diameter of these hobs as small as possible. In the one-piece form of hob, in which the hob and its shaft are made in a single integral piece, the cost of making is very high compared to cost of ,making the shell form, as the steel employed is of expensive character.

Another disadvantage in hobs of the one-piece type is that they are apt warp during the tempering op-, erations. Furthermore, they are usually made of small diameter and have a less number of teeth than the shell form.

The object of my invention is to provide a hob which will combine the advantages of the shell and one-piece types, while overcoming the disadvantages of both these types.

UTTER.

Letters n Patented May 12, 1914. 1912. Serial No. 713,556.

the spirit and scope of my invention as de fined in the appended claims.

In these drawings, the numeral 2 designates the body of the hob, having helically arranged cutting teeth 3. Each of these teeth has its periphery. shaped to give an additional peripheral cutting edge. This feature of my invention forms thesubject-matter of my eopending application Serial N 0. 740,926, filed January 9, 1913. p

The main cutting edge of each tooth is designated at a and the supplemental cuttingedge at b. The two cutting edges are at the same radial distance from the center of the hob, and are backed off to form the respective clearances a, b.

3 designates the backing off at the sides of the teeth.

The hob body 2 is made solid, except that I preferably form centrally therethrough a small longitudinal opening 5, for the purpose hereinafter described. It is provided at one end with the extension 6, which is cylindrical at its end portion, but is squared adjacent to the end face of the hob, as shown at 6*. At the other end it has a cylindrical extension 7, which is adapted to engage a socket in the enlarged inner end portion of a follower 9. The squared portion 6 of the extension 6 is adapted to fit the squared walls 10 of a socket in one end of the driving member at 11. The inner end portion of this socket is, however, made cylindrical, as shown at 10 in order to receive the cylindrical portion of the extension 6 beyond its squared portion 6 The driving member 11 is provided with a tapered driving extension 12, which is adapted to be seated in a similarly shaped opening in a driving spindle on the machine tool on which the cutter is used.

13 designates the tie bolt, which is inserted through the follower 9 and through the central opening of the hob body, its end be ing threaded for engagement with the threaded opening in the driving member 11. While this tie rod may be omitted, it forms a simple and convenient tie connection between the parts. As its only function is The nature of my invention will be best "that of a tie, it can be made of a relatively small diameter, so that only a small opening is required in the hob body to receive it. This Opening can be made of such small diameter as not to materially weaken the hob.

In Fig. 8 I have shown a modification of my invention in which the tie rod is omitted. In this figure corresponding parts are given the same numerals as in the figures first described, with the letter I) added thereto. In this construction, the body 2* of the hob is made without any opening therethrough, its end projections 6 7 having a driving fit with the sockets of the members 8 and 11 15 designates the driving connection for the member 11*; and 16 and 17 designate the usual bearings. It will be readily seen that the parts are confined between the two bearings 16 and 17 in a manner to prevent any longitudinal separation thereof, notwithstanding the absence of a tie rod.

My invention enables the provision of a hob of small diameter, in which the hob body carrying the cutting edges can be made from a high grade of steel, while the supporting members can be made from a lower grade of steel. It also provides means of simple character for securing the parts together so as to form a practically one-piece device.

I claim 1. A hob body having an axial projection at one end, and a separate driving member formed with a socket at its inner end port-ion,whicl1 socket has a driving engagement with said projection, substantially as described.

2. A hob body having an axial projection at each end, a separate driving member formed with a socket at its inner end, which socket has a driving engagement with one of said projections, and a separate follower member having a socket engaging the other axial projection, substantially as described.

3. A hob body'having an axial projection at each end and a separate driving member formed with a socket at its inner end, which socket has a driving engagement with one of said projections, and a separate follower member-having a socket engaging the other axial projection, together with a tie member extending through the follower member and hob member and detachably engaged with the driving member, substantially as described.

4. A hob comprising a hob body, a sepa-' rate driving member having a driving engagement with one end of the body, a sepa rate follower member engaged with the other end of the hob body, and a tie member connecting said parts, substantially as described.

In testimony whereof, I have hereunto set my hand.

THOMAS FAWCUS.

Witnesses JEssE B. HELLER, H. M. CoRwIN. 

